10 advanced PHP interview questions and answers for 2023

"PHP Extension and Application Repository" (PEAR) is an acronym for "PHP Extension and Application Repository." PEAR is a framework and repository for any PHP components that can be reused.

For web developers, PEAR enables a higher level of programming. It's jam-packed with PHP code snippets and libraries. It also has a command-line interface for installing packages automatically.

When naming a PHP variable, you must follow the following two rules:

• A variable must start with a dollar sign and end with the variable's name. For instance, $price=100; where the price is the name of a variable.
• A letter or an underscore must be the first character in a variable name.
• Letters, digits, and underscores can all be used in a variable name. Spaces and special characters are not permitted instead of a PHP variable.
• Variables in PHP are case-sensitive. As a result, $NAME and $name are both handled as distinct variables.

PHP scripts can generate HTML, and information can be passed from HTML to PHP. HTML is a client-side language, while PHP is a server-side language. So PHP runs on the server and returns texts, objects, and arrays, which we then utilize to display the values in HTML. This engagement aids in bridging gaps and the effective usage of both languages.

A PHP parser is a piece of software that translates source code into computer-readable code. The parser converts whatever set of instructions we provide in the form of PHP code into a machine-readable format. The token gets all() functions in PHP that can be used to parse PHP code.

Traits are a method that allows you to write reusable code in PHP and other languages that don't support multiple inheritances. It isn't possible to create it by itself.

A trait is designed to overcome the limits of sole inheritance by allowing a developer to easily reuse sets of methods across many independent classes in distinct class hierarchies.

Hashing a password is a method of transforming a single password into a hashed password string. The hashed password is usually one-way, meaning we can't move from the hashed password to the original password. So the question is why we needed to utilize hashing to perform all of this; why do extra work when we can just record our passwords as a simple string in the database? All of this is being done just to improve security so that hackers do not steal credentials from our valued site. md5, crypt, sha1, and bcrypt are some of the most often used cryptographic algorithms in PHP. The bcrypt hashing algorithm is the most widely used presently.

The primary types of errors are:

• Notices: Notices are non-critical errors that can occur while the script is being executed. Users won’t see these. Using an undefined variable as an example.

• Warnings: Warnings are more important than notices. The script execution is not interrupted by warnings. These are viewable by default. Include() a file that does not exist, for example.

• Syntax or Parsing error:- A forgotten quote mark, a missing semicolon at the end of a line, missing parenthesis, or excess characters are all examples of syntax errors. The PHP parser is unable to read and comprehend the code correctly, resulting in a parse error.

• Fatal: This is the most serious error of kind, and when it happens, the script's execution is immediately terminated. An example of a fatal error is accessing a non-existent object's property or calling need() on a non-existent file.

A cookie is a tiny file placed on the client's computer by the server. They keep track of a user's information in the browser. When a user requests a specific page, it is embedded on the user's machine and used to identify them. When a comparable PC requests a website with software, the cookie is sent as well.

Cookies save the session id produced at the back end after authenticating the user's identity in encrypted form. It must be stored in the machine's browser. Because you cannot access any object across the website or web apps, you can only store string values.

Cookies are URL-specific by default. Gmail cookies, for example, are not supported by Yahoo, and vice versa. By default, cookies are ephemeral and transitory. A single website or web app can create up to 20 cookies per site. The cookie's initial size is 50 bytes, while the cookie's maximum size is 4096 bytes.

Setcookie() function is used for making a cookie in PHP.

The 4 primary steps used to create a new MySQL database in PHP are given below:

• The PHP script is used to establish a connection to the MySQL server.
• The connection has been verified. You can test the connection by writing an example query.
• The queries for the database are typed in and then saved in a string variable.
• Then, one by one, the constructed queries will be run.

PHP Data Object (PDO) is an acronym for PHP Data Object. PDO is a PHP extension that includes a core PDO class as well as database-specific drivers. Any database written for the PDO driver can be accessed using the PDO extension. PDO drivers are available for databases such as FreeTDS, Microsoft SQL Server, IBM DB2, Sybase, Oracle Call Interface, Firebird/Interbase 6, and PostgreSQL.

It provides a data-access abstraction layer that is lightweight and vendor-neutral. As a result, the function to issue queries and fetch data will be the same regardless of which database we utilize. It also concentrates on data access abstraction rather than database abstraction.